Electrochemical apparatus with adjustable electrode



Get. 17, 1950 Fil d Nov. 1, 1946 5 an E L. H. PECK ELECTROCHEMICALAPPARATUS WITH ADJUSTABLE ELECTRODE 2 Sheets-Sheet 1 .z -5. ia

Oct. 17, 1950 H. PECK 5, 38

ELECTROCHEMICAL APPARATUS WITH C ADJUSTABLE ELECTRODE FilQ -Noy. 1-,1946 2 Sheets-Sheet 2 3 HAM/MM Zee/Zfka',

Patented Oct. 17, 1950 ELECTROCHEMICAL APPARATUS WITH ADJUSTABLEELECTRODE Lee H. Peck, Chagrin Falls, Ohio, assignor, by mesneassignments, to Koppers Company, Inc., a corporation of DelawareApplication November 1, 1946, Serial'No. 707,066

12 Claims.

The present invention relates to an automatic or semi-automatic devicefor use in the striking or initiating of electrical discharges.

In the electrochemical transformation of a gas eous medium in thepresence of an electrical discharge between a single pair of electrodes,it is necessary to strike or initiate the discharge using an appropriatestriking voltage; for example, with a high frequency discharge of 2.1megacycles, the striking voltage for a 17 mm. (millimeter) gap may beapproximatel 18,000 volts; whereas, after the discharge has been struckthe active operating voltage is only about thereof or about 1800 volts.The figures given are for the production of hydrazine from ammonia inwhich the electrochemical transformation of the ammonia is carried outat super-atmospheric pressures, as for example, 770 mm.

In the manufacture of nitric oxide from atmospheric air atsub-atmospheric pressures, as for example, at 335 mm. pressure, for a1'? mm. gap, the striking voltage may approximate 25% to 3000 volts.After the discharge is-once struck, the active operating voltage. mayvary approximately between 1000 and 1200 volts.

It is well known that other conditions remaining constant, the strikingvoltage or breakdown voltage in a gaseous discharge is approximatelyproportionate to the gap distance, that is, the distance betweencooperating electrode terminals between which the discharge isinitiated. Therefore, if the gap between a cooperating pair ofelectrodes can be temporarily decreased at the time the discharge isstruck, the striking voltage may be proportionately decreased, and ifthe gap be decreased so that the striking voltage does not exceed thenormal operating voltage, the electrode discharge gap after thedischarge is struck may be lengthened or drawn out to a desiredpredetermined gap which is the original electrode the electrochemicaltransformation of a gaseous medium' comprising the combination of areactor vessel, a pair of electrode terminals positioned.

able electrode terminal to its initial position or any otherpredetermined position, means being provided for introducing a' gaseousmedium into said casing while maintaining a relatively higher pressureabove the plunger than therebelow to move the piston and its electrodeterminal closer v to the cooperating electrode and shorten theelectrode: gap between the electrode terminals so that the dischargetherebetween maybe effected under operating voltage instead of underhigher striking voltage, there also being provided means" for reducingthe' press'ure diiieren'tialbetween the pressures above and below theplunger to substantially zero, whereupon the returning means returns thereciprocating electrode to a prede.

termined position. i

It is an additional object of the invention to provide means to leakgaseous medium from, above the plunger to below the plunger to equalizethe pressure'above and below the plunger whereupon th'e returning meansreturns the recipro cating electrode to a predetermined position;

While spring means may be employed to return the adjustable orreciprocating electrode other equivalent means maybe employed.

It is an additional object of the present inven tion to provide anapparatus of the character set forth wherein the adjustable electrode iscaused to reciprocate to shorten the electrode gap be tween itscooperating electrode by the applica-, tion of a super-atmosphericpressure which may be just slightly above atmospheric pressure or may beconsiderably higher.

It is an additional-object of the present invention to utilize apressure lower than atmospheric to cause the adjustable electrode of theapparatus to reciprocate to shorten the electrode gap.

The invention will be described in connection with the accompanyingdrawing wherein Figure 1 isthe-frontelevation of the electrode gapadjusting device;

Figure 2 is a plan view thereof. 1 1

Figure 3 is a longitudinal cross sectional view taken on line 33 ofFigure 2.

Figure 4 is a detail view of the plunger of the electrode gap adjustingdevice.

Figure 5 is a longitudinal sectional view showing the piston member ofthe electrode gap adjustor in its depressed condition adapted toposition the electrode for the shortest electrode gap.

Figure 6 is a view partly in section of the electrode gap adjustorassembled with an electrical discharge reactor adapted to eifectelectrochemical transformation of a gaseous medium undersuper-atmospheric pressure.

Figure '7 is a similar view wherein the electrochemical transformationof the gaseous medium is effected. at sub-atmospheric pressure.

Referring to the drawing, the electrode adjustor comprises a casing It]provided with a member II which functions as an inlet member whenoperating under super-atmospheric pressure and as an outlet member whenoperating at sub-atmospheric pressure. The casing I0 is provided with aninner wall l2, and at its lower extremity, it is rovided with a bottomwall l3, the latter acting to limit the travel stroke of the plunger l4in a manner as hereinafter set forth. The casing adjacent its lowerextremity is provided with a series of apertures l 5, l6, l1, and I8,adapted to allow the gaseous medium which operates the device to escapefrom the casing while the piston l4 has been depressed. The casing atits upper portion is provided with a conductive cap l9 provided with atop wall '20 and a lower wall 2|, the latter functioning to limit theupward stroke of the piston 14. The cap, which is externally threaded at22 is screwed into the upper end of the casing which is provided withthreads 23. A binding post 24 adapted to receive the electricalconnector 25 is connected with the upper wall member 20.

The piston rod 14 is provided with a lower cylindrical portion 26, anintermediate enlarged cylindrical portion 21, and a top cylindricalportion 29. The cylindrical portion 2'! is provided with a shoulder 28at its juncture with the piston rod portion 26. The shoulder portion 28serves as a stop to limit the downward stroke of the piston rod [4.

Adjustably mounted on the piston rod I4 is the piston or plunger 30which is held in a predetermined position by the screw nut 32. Thepiston rod l4 below the plunger 30 is provided with a coil spring 33. Itis to be noted that the coils of the spring 33 are not of the samediameter throughout the spring, but that the coils of smaller diameterare at the top portion of the spring, and the coils gradually increasein diameter from the upper portion of the spring towards the lowerportion of the spring. This is the preferred type of spring as itoperates to exert its pressure at and adjacent the center of the plunger30 instead of adjacent the periphery of the plunger 30. When the springpressure is exerted at and adjacent the periphery portion of the pistonor plunger 30 there is a tendency for the piston to jam in the casing,and this is eliminated by the employment of a spring of the characterset forth.

It is to be noted that preferably there is a small clearance between theouter surface 3| and the interior wall of the casing III. This clearanceshould be sumcient to allow the escape or leakage of gases past thepiston plunger after the gas has acted to effect movement of the pistoneither in a downwardly or upwardly direction, depending on whether theactivating gas is at superatmospheric pressure or at sub-atmosphericpressure, respectively.

The lower portion of the piston member 26 is threaded at 31 and isadapted to receive the electrode terminal 38. The piston rod l4,including the lower portion 26, acts as one electrode for the reactor 40in which there is positioned a cooperating electrode terminal 39 and anelectrode 4 I.

The upper end of the reactor 40 is provided with an apertured closuremember 42 preferably of a non-conducting material in which the electrodeadjustor E is mounted. The lower end of the reactor is provided with anon-conducting closure member 43.

Means are provided to introduce the gaseous medium to beelectrochemically transformed into the reactor 40, a suitable inletmeans such as the conduit 44 being provided.

Connected to the inlet conduit 44 are branch lines 45 and 43. At thejunction of conduits 44, 45, and 46, there is provided a three-way valve41. The conduit 45 is connected to the conduit H of the electrodeadjustor E.

For operation under super-atmospheric conditions the hookup set forth inFig. 6 is suitable. In starting operations the normal operation voltage,as for example 1800 volts, suitable for the production of hydrazine fromammonia is applied to the electrode terminals 38 and 39. Thereafter thevalve 41 is positioned so asto allow the gas to be transformed, such asammonia, to pass by the way of the conduit 45 and conduit H into theinterior of the electrode adjustor E where it acts upon the plunger 30causing the piston rod 26 to move downwardly to the position shown inFigure 5 where the electrode terminal 38 is closely adjacent theelectrode terminal 39.

In the specific case set forth the electrode terminal 38 has been moved16 mm. inwardly to within 1 mm. of the terminal 39. With this shortenedelectrode gap the discharge strikes at a very low voltage, as forexample, for the production of ammonia from hydrazine, at 1800 voltsinstead of 18,000 volts. As soon as the discharge has been effected thevalve 41 is turned to cause the incoming gas to fiow through the conduit46 into the interior of the reactor 40 whereupon the pressure within thereactor causes the gas to flow through the small apertures I5, 16, H,and I8 into the interior of the casing [0 below the plunger 30, therebyequalizing the pressures below and above the plunger 30. When thisoccurs, the spring 33 forces the plunger upwardly and thereby causes therod 26 to move upwardly and restore the electrode terminal 38 to itsoriginal predetermined position 17 mms. from the electrode terminal 39,or to any other desired position.

In the above form of the invention when utilizing super-atmosphericpressure the operation is semi-automatic, and it is not necessary tohave any substantial clearance between the exterior surface 3| of theplunger 30 and the interior wall of the casing l0. However, in the formof the invention shown in Figure '7, the electrode gap adjustor may bemade to function fully automatically by providing and utilizing aclearance space. The electrochemically transformed product passes fromthe reactor 40 through the conduit 50.

Referring to Figure '7, the electrochemical transformation of thegaseous medium is carried out under sub-atmospheric pressure, as forexample, under a pressure of 335 mm. when electrochemically transformingatmospheric air to nitrogen oxide.

The reactor 30 is provided with an inlet conduit 49 and an outletconduit 50 connected to the vacuum pump P. A by-pass conduit 52 isconnected to the conduit l l of the electrode adjuster E and to theoutlet 50 via the valve 5|.

In operation the normal operating voltage, as

for example, 1000 to 1200 volts, is applied to the electrode connector25 and the electrode 4|. The applied voltage is, as stated, theoperating voltage of 1000 to 1200 volts, and not the striking voltage of5000 to 6000 volts which would be required if the electrode adaptor Ewere not u ilized.

Thereafter, the vacuum generated by the vacuum pump P is applied to theconduit 50, the valve 5! being so set as to disconnect the by-passconduit 52. As soon as this vacuum is established, atmospheric air to btransformed enters the reactor 40 by means of the conduit 49, and thevacuum is communicated to the interior of the casing in via theapertures l5, l6, l1, and I8. The gaseous medium under a vacuum pullsthe plunger downwardly compressing the spring 33 and forcing electrodeterminal 33 inwardly 16 mms. to within 1 mm. of the electrode terminal39. After the discharge has been struck, the electrode 38 is broughtback to its predetermined normal position in the following manner whichis automatic.

As previously stated, there is a clearance between the periphery of thepiston 30 and the interior wall of the casing Hi. The air in the easingI above the plunger 30 before the plunger moved downwardly under theaction of the vacuum is at atmospheric pressure and is at all times at apressure higher than that existing in the gaseous medium below theplunger. As soon as the plunger 30 is pulled downwardly on applicationof the vacuum the discharge strikes, and the leakage of the gaseousmedium from the space above the plunger to the space below the plungeris initiated, thus starting the reverse or upward movement of theplunger. The time for the reverse] is dependent upon the tension of thespring and the clearance of the plunger.

When operating as herein set forth, the time of reversal may take about10 seconds. It is desired to point out, however, that it is not desiredto be limited to this time period as the time period can be adjusted toany desired reversal time by the tension of the spring and the clearancebetween the plunger 30 and the interior wall of the casing l0.

It is to be noted that the operation as above set forth is fullyautomatic and the valve remains positioned as shown in Fi ure '7. If aquick reversal is required the valve 5|, which is normall closed, ismomentarily opened, whereupon the pressures above and below the plungerare rapidly equalized as, for example, in a fraction of a second. Inthis case the operation is semiautomatic.

Referring to Figure 6, a gaseous medium under a pressure varying from770 mm. to 800 mm. is introduced into the casing in above the plunger30, and then the arc is struck at the normal operating voltage which asstated, is much lower than the usual striking voltage. Thereafter, thesame gas or a different gas is introduced by a conduit 36 and passesthrough the openings I5, l6, l1, and I8 into the casing below thepiston. Upon the pressure being equalized, the piston 30 is caused totravel upwardly under the influence of the spring 33 which has beencompressed duringthe downward stroke of the piston. Instead of using thesame pressures above and below the piston 30 to operate the piston inthe manner above set forth after the plunger 30 has oncebeen depressed,the gas introduced below the piston may have a higher pressure in poundsper sq. in. than pheric pressure, and the valve 5| is closed.Theoperations are started, and the normal operating voltage is appliedbetween the electrode terminals 38 and 39. Thereafter with the valve 5!closed,

the vacuum is applied in the manner hereinbefore set forth.

It is desired to point out that in the form of the apparatus shown inFigure 7, instead of having a gas at atmospheric pressure in the casingl0 above the plunger 30, the gas may be at below atmospheric pressureand a gas at a pressure still lower than the pressure of the gas in thecasing abovev the piston may be introduced into the casing below thepiston to cause the piston to operate. The point, again, is that evenwhen operating under a vacuum all that is necessary is that there be a"difference in pressure above and below the piston in order to activatethe piston and shorten the electrode gap. After the electrode gaphasbeen shortened, the pressure is equalized, and upon equalization, thespring 33 effects return of the adjustable electrode to a predeterminedposition.

The difference in pressures must be suflicient to overcome the pressureexerted by the upward thrust of the spring.

I claim:

1. In an electrode gap adjustor, the combina tion of a casing having aninterior chamber, a

top end wall, and an-aperturedlower end wall, a piston carrying aplunger intermediate its upper and lower end, the latter being providedwith an electrode terminal, said piston reciproeating, in said chamberthrough the 'apertured' lower end member, stop means on said pistonv andreciprocating therewith, auxiliary cooperat-' ing stop means in saidcasing for limiting the forwardstroke of the piston to the. distanceitis desired to move the electrode terminal, spring means in said casingpositioned to assist in re turning the plunger, the piston, and theelectrode terminal after completion of the forwardstroke of the piston,means tolimit the upward travel u of the piston and the electrodeterminal, and means for effecting reciprocation of the plunger in thechamber casing including an opening in' the casing below the plunger;

2. In an electrode gap adjuster, the combination of a casing having aninterior chamber, a top end wall, and an apertured lower end wall,

a piston carrying a plunger intermediate its,

upper and lower end, the latterbeing provided with an electrodeterminal, said piston reciprocating in said chamber through theapertured lower end, a clearance space between said plunger and theinterior wall of the casing chamben'stop,

means on said piston and reciprocatingtherewith, auxiliary cooperatingstop means in said casing for limiting the forward stroke of the V The ppiston to the distance it is desired to move the electrode terminal,spring means in said casing positioned to assist in returning theplunger, the piston, and the electrode terminal after completion of theforward stroke of the piston, means to limit the upward travel of thepiston and the electrode terminal, and means for effecting reciprocationof the plunger in the chamber casing including an opening therein.

3. In an electrode gap adjustor, the combination of a casing having aninterior chamber, a removable upper cap having an interior bottom walland an apertured lower end wall, the interior wall of which acts as astop member, a piston carrying plunger intermediate its upper and lowerend, the latter being provided with an electrode terminal, said pistonreciprocating in said chamber through the apertured lower end wall, stopmeans on the piston and reciprocating with the piston, said stop meansabutting the interior lower end wall and limiting the forward stroke ofthe piston the distance it is desired to move the electrode terminal,spring means positioned in said casing below said plunger to assist inreturning the plunger, the piston, and the electrode terminal aftercompletion of the forward stroke of the piston, means to limit theupward travel of the piston and electrode terminal comprising theinterior bottom wall of the cap member, and means for eifectingreciprocation of the plunger in the chamber casing, including an openingin the casing below the plunger.

4. In an electrode gap adjustor, the combination of a casing having aninterior chamber, a removable upper cap having an interior bottom walland an apertured lower end wall, the interior wall of which acts as astop member, a piston carrying a plunger intermediate its upper andlower end, the latter being provided with an electrode terminal, saidpiston reciprocating in said chamber through the apertured lower endwall, stop means on the piston and reciprocating with the piston, saidstop means abutting the interior lower end wall and limiting the forwardstroke of the piston the distance it is desired to move the electrodeterminal, spring means positioned in said casing below said plunger toassist in returning the plunger, the piston, and the electrode terminalafter completion of the forward stroke of the piston, means to limit theupward travel of the piston and electrode terminal comprising theinterior bottom wall of the cap member, and means for effectingreciprocation of the plunger in the chamber casing, including aplurality of small openings positioned circumferentially of the casingadjacent its lower end.

5. In an electrode gap adjustor, the combination of a casing having aninterior chamber, a removable upper cap having an interior bottom walland an apertured lower end wall, the interior wall of which acts as astop member, a piston carrying a plunger intermediate its upper andlower end, the latter being provided with an electrode terminal, saidpiston reciprocating in said chamber through the apertured lower endwall, stop means on the piston and reciprocating with the piston, saidstop means abutting the interior lower end wall and limiting the forwardstroke of the piston the distance it is desired to move the electrodeterminal, spring means positioned in said casing below said plunger toassist in returning the plunger, the piston, and the electrode terminalafter completion of the forward 8 stroke of the piston, means to limitthe upward travel of the piston and electrode terminal comprising theinterior bottom wall of the cap member, means for effectingreciprocation of the plunger in the chamber casing, including an openingin the casing below the plunger, and means to leak gaseous medium fromabove the plunger to below the plunger to equalize the pressure aboveand below the plunger.

6. In an electrode gap adjustor, the combination of a casing having aninterior chamber, a removable upper cap having an interior bottom walland an apertured lower end wall, the interior wall of which acts as astop member, a piston carrying a plunger intermediate its upper andlower end, the latter being provided with an electrode terminal, saidpiston reciprocating in said chamber through the apertured lower endwall, stop means on the piston and reciprocating with the piston, saidstop means abutting the interior lower end wall and limiting the forwardstroke of the piston the distance it is desired to move the electrodeterminal, spring means positioned in said casing below said plunger toassist in returning the plunger, the piston, and the electrode terminalafter completion of the forward stroke of the piston, means to limit theupward travel of the piston and electrode terminal comprising theinterior bottom wall of the cap member, means for effectingreciprocation of the plunger in the chamber casing, including aplurality of small openings positioned circumferentially of the casingadjacent its lower end, and means to leak gaseous medium from above theplunger to equalize the pressure above and below the plunger.

7. In a gas-discharge apparatus for effecting electrochemicaltransformation of a gaseous medium under super-atmospheric pressure, thecombination of a reactor vessel, a pair of electrode terminalspositioned respectively on a pair of lectrode members, eaid electrodeterminals being capable of effecting an electrical discharge in saidreactor, one of said electrode members and its electrode terminal beingmounted on a piston reciprocating in a casing to vary the electrode gapbetween said electrode terminals, means for introducing a gaseous mediumunder pressure into said casing to move said piston and its electrodeterminal closer to the cooperating terminal and initiate a dischargebetween the electrode terminals at a lower operating voltage than isrequired in the absence of the shortening of the electrode gap, meansfor introducing a gaseous medium to be transformed into the reactorvesselunder super-atmospheric pressure, means including an opening inthe casing for returning the reciprocating electrode to a predeterminedposition, and means for removing the transformed reaction product fromthe reactor vessel.

8. In the gas-discharge apparatus for effecting the electrochemicaltransformation of a gaseous medium under super-atmospheric pressure, thecombination of a reactor vessel, a pair of electrode terminalspositioned respectively on a pair of electrode members, said electrodemembers being capable of effecting an electric discharge in saidreactor, one of said electrode members and its electrode terminals beingmounted on a piston provided with a plunger held in an initialpredetermined position by spring means, said piston and plungerreciprocating in a casing to shorten the electrode gap between saidelectrode terminals, means including an opening in the casing forintroducing a gaseous medium under pressure into said casing to movesaid piston and its electrode terminal closer to itscooperatingterminal, and shorten the electrode gap between saidterminals and initiate a discharge between the electrode terminals at alower operating voltage than is required in the absence of theshortening of the electrode gap, means including an opening in thecasing for introducing a gaseous medium into the reactor vessel undersuper-atmospheric pressure and into the casing below said plungerwhereupon the pressure below and above the plunger becomes equalized andthe spring means returns the reciprocating electrode to a predeterminedposition, and means for removing a gaseous product from the reactionvessel.

9. In the gas-discharge apparatus for effecting the electrochemicaltransformation of a gaseous medium, the combination of a reactor vessel,a pair of electrode terminals positioned respectively on a pair ofelectrode members, said electrode members being capable of effecting anelectric discharge in said reactor, one of said electrode members andits electrode terminals being mounted on a piston provided with aplunger held in initial predetermined position by spring means, saidpiston and plunger reciprocating in a casing to shorten the electrodegap between said electrode terminals, means for introducing a gaseousmedium under a vacuum into the reactor vessel, an opening in said casingfor introducing gaseous medium therein to move said piston and itselectrode terminal closer to the cooperating electrode terminal andshorten the electrode gap between said electrode terminals and initiatea discharge between the electrode terminals at a lower operating voltagethan is required in the absence of the shortening of the electrode gap,means for equalizing the pressure of the gaseous medium above and belowthe piston plunger, means acting upon said equalization of pressure forreturning the reciprocating electrode terminal to a predeterminedposition, and means for removing the gaseous product from the reactorvessel.

10. In a gas-discharge apparatus for effecting the electrochemicaltransformation of a gaseous medium, the combination of a reactor vessel,a pair of electrode terminals positioned respectively on a pair ofelectrode members, said electrode members being capable of effecting anelectric discharge in said reactor, one of said electrode members andits electrode terminals being mounted on a piston provided with aplunger held in an initial predetermined position by spring means, saidpiston and plunger reciprocating in a casing, to shorten the electrodegap between said electrode terminals, means for introducing a gaseousmedium under a vacuum into the reactor vessel, an opening in said casingfor introducing gaseous medium therein, to move said piston and itselectrode terminal closer to the cooperating electrode terminal andshorten the electrode gap between said electrode terminals and initiatea discharge between the electrode terminals at a lower operating Voltagethan is required in the absence of the shortening of the electrode gap,means for removing the gaseous product from the reactor vessel, means toleak gaseous medium from above the plunger to below the plunger toequalize the pressure above and below the plunger whereupon the springmeans returns the reciprocating electrode to a predetermined position,and -means for removing the gaseous product from. the reactor vessel.

11. In a gas-discharge apparatus for effecting the electrochemicaltransformation or" a gaseous medium, the combination of a reactorvesseha pair of electrode terminals positioned respectively on a pair ofelectrode members, said electrode members being capable of effecting anelectric discharge in said reactor, one of said electrode members andits terminals being mounted on a piston provided with a plunger held inan initial predetermined position by spring means, said piston andplunger reciprocating in a casing to shorten the electrode gap betweensaid electrode terminals, an opening in said casing, means forintroducing a gaseous medium through said opening into said casing,while maintaining a relatively higher pressure above the plunger thanbelow, to move the piston and the electrode terminals against the springmeans and bring'said electrode terminal closer to its cooperatingterminal, to thereby shorten the electrode gap between said terminalsand initiate a discharge between the electrode terminals at a loweroperating voltage than is required in the absence of the shortening ofthe electrode gap, means for reducing the pressure differential aboveand below the plunger to substantially zero, whereupon the spring meansreturns the reciprocating electrode to a predetermined position, andmeans for removing the gaseous product from the reactor vessel.

12. In the gas-discharge apparatus for efiecting the electrochemicaltransiormation of agaseous medium, the combination of a reactor vessel,a pair of electrode terminals positioned respectiveiy on a pair ofelectrode members, said electrode members being capable oi efi'ecting anelectric discharge in said reactor, one of said electrodemembers and itselectrode terminals being mounted on a piston provided with a plungerheld in initial predetermined position by spring means, said piston andplunger reciprocating in a casing to shorten theelectrode gapbetweensaid elecating voltage than is required in the absence of a shorteningof the electrode gap, means for equalizing pressure or" the gaseousmedium above and below the piston plunger, means acting upon saidequalization of pressure for returning therecipro-p eating electrodeterminal to predetermined position and means for removing a gaseousproduct from the reactor vessel.

LEE H. PECK.

REFERENCES CITED' I The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 758,884 Alsop May 3, 19041,039,851

Wagener a. Oct. 1, 1912,

11. IN A GAS-DISCHARGE APPARATUS FOR EFFECTING THE ELECTROCHEMICALTRANSFORMATION OF A GASEOUS MEDIUM, THE COMBINATION OF A REACTOR VESSEL,A PAIR OF ELECTRODE TERMINALS POSITIONED RESPECTIVELY ON A PAIR OFELECTRODE MEMBERS, SAID ELECTRODE MEMBERS BEING CAPABLE OF EFFECTING ANELECTRIC DISCHARGE IN SAID REACTOR, ONE OF SAID ELECTRODE MEMBERS ANDITS TERMINALS BEING MOUNTED ON A PISTON PROVIDED WITH A PLUNGER HELD INAN INITIAL PREDETERMINED POSITION BY SPRING MEANS, SAID PISTON ANDPLUNGER RECIPROCATING IN A CASING TO SHORTEN THE ELECTRODE GAP BETWEENSAID ELECTRODE TERMINALS, AN OPENING IN SAID CASING, MEANS FORINTRODUCING A GASEOUS MEDIUM THROUGH SAID OPENING INTO SAID CASING,WHILE MAINTAINING A RELATIVELY HIGHER PRESSURE ABOVE THE PLUNGER THANBELOW, TO MOVE THE PISTON AND THE ELECTRODE TERMINALS AGAINST THE SPRINGMEANS AND BRING SAID ELECTRODE TERMINAL CLOSER TO ITS COOPERATING TER-